Redundant quotes in `subprocess.TimeoutExpired` message

Bug report

Bug description:

Bug description:

While looking into https://github.com/python/cpython/pull/151486, I noticed a similar issue in subprocess.TimeoutExpired.__str__.

subprocess.TimeoutExpired.__str__ manually wraps cmd in single quotes while formatting the exception message.
This produces confusing output when cmd is a list, because the list representation already contains quotes around its string elements.

import subprocess
import sys

cmd = [sys.executable, "-c", "import time; time.sleep(10)"]
subprocess.run(cmd, timeout=0.01)

Current output:

Traceback (most recent call last):
  ...
subprocess.TimeoutExpired: Command '['...python...', '-c', 'import time; time.sleep(10)']' timed out after 0.01 seconds

Expected output:

Traceback (most recent call last):
  ...
subprocess.TimeoutExpired: Command ['...python...', '-c', 'import time; time.sleep(10)'] timed out after 0.01 seconds

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-152559

从 subprocess.TimeoutExpired.str 开始，检查现有的 subprocess 异常测试。重现 timeout 示例，调整预期消息，使命令表示不会被重复包裹，并验证相关的 subprocess 测试通过；关联的 PR gh-152559 表明相关工作已经在进行中。